Puffed pork skins have been a popular snack food for many years. This snack food has its genesis from "cracklings" which was a solid product resulting from conventionally-practiced rendering processes. Hog fat or lard is rendered by applying heat to melt the fat and to drive water out of the tissue. After the melted fat is drained away, the remaining solid portions of the tissue are compressed, while hot, to squeeze out additional fat. This solid, compressed product of non-fat tissue is called "cracklings" because of the brittle nature of that product. With time, the more-usually practiced technology for producing lard changed and the avalability of "cracklings" decreased, while the demand for "cracklings" increased.
A snack food which is similar to "cracklings" is prepared by cutting pork skins into strips, rendering and deep-fat frying those strips at high temperatures until the strips are puffed. While this process is the conventionally practiced process, it does have problems associated therewith which have long plagued the art. The availability of pork skins changes from time to time, as well as the quality thereof, and the conventional process can not acceptably accomodate significant variations in the starting material, since unacceptable product, e.g. a tough product, may result. The process produces substantially quantities of small rendered pieces (called fines, balls and tails -- depending on the size and shape) which cannot be puffed into an acceptable product and is therefore wasteful of starting material. The process is somewhat time-consuming and, hence, substantially increases the cost of the product.
The art has long sought processes to obviate one or more of these problems. For example, U.S. Pat. No. 2,547,747 proposes to use bacon rinds instead of skins and the rinds are steam-cooked, ground, and extruded into strips which are subsequently cut in appropriate sizes and deep-fat fried or baked to puff the strips. Somewhat similarly, U.S. Pat. No. 2,562,850 suggests that a high pressure steam cooking be carried out until the bacon rind is gelatinized, and, after pressing to remove the remaining fat, the gelatinized mass is formed into sheets, cut, and then deep-fat fried or baked.
In U.S. Pat. No. 2,947,635, the toughness often associated with some puffed pork skins is attributed to inadequate moisture removal in the frying step which result from the collapse of puffed cells in the fried skin. To avoid this difficulty, it is proposed that the frying take place by means of differential pressure processing, e.g., the frying step being carried out in deep fat maintained in a vacuum system.
On the other hand, U.S. Pat. No. 2,907,660 teaches that the difficulty is due to varying moisture contents of the pork skins (including bacon rinds and green skins), even after an initial rendering step. This also results in variable properties of the fried skins. That patent suggests heating the skins in hot oil until all visible vapor is removed and then further heating the skins in that oil under pressurized conditions of up to 20 psi. That intermediate product is then said to be uniform in moisture content and will produce uniform puffed skins.
A somewhat similar process is described in U.S. Pat. No. 3,401,045, where green pork skins are cut and rendered in fat at higher temperatures for extended periods of time, i.e., until the green skins are cooked and are reduced in size to about one-half of the original size. These relatively hard, dry and tough pieces are then soaked in an aqueous flavoring solution, dried to the proper moisture content and puffed by deep-fat frying.
A similar idea is stated in U.S. Pat. No. 3,428,462, which proposes low-rendering temperatures for initially cooking green pork skins, with increasing fat temperatures and the repeated addition of water to the fat vessel until the green skins are finally cooked and puffed at the higher temperatures of the latter portions of the process. This is said to supply the necessary moisture for the skins and avoid the difficulty of hard and impalatable product.
As can be easily appreciated from the foregoing, the art has long struggled with the difficulties in the conventional process and many different ideas about alternative starting materials and the causes of the difficulties and the means of obviating those difficulties have been proposed. One common factor that stands out, however, is the difficulty of obtaining uniform starting materials. The conventional process is not well adapted to handle a variety of starting materials and these various different starting materials have necessitated a number of different and mutually distinct processes. Of course, however, changing a manufacturing process each time the starting material changes is not practical. Thus, from a practical point of view only the use of pork skins as the starting material has achieved any substantial commercial success, even though this conventional process continues to have the problems discussed above.
This problem has recently been accentuated by the popularity of pigkin leathers for shoes, garment decorations, and the like, which has severely limited the amount of green pork skins available for processing into the snack food. Further, the increased popularity of bacon having the rind thereon has decreased the availability of bacon rinds for the less desirable but alternative process. As a result, efforts have been made to utilize animal parts, other than pork skins, for producing the snack food, but these efforts, of course, introduce even more variability of starting material than the variability of the pork skins which has long plagued the art, as discussed above. However, in view of the shortage of all of green pork skins, bacon rinds, and rendered skins, it would be a decided advantage to the art to provide processes for handling variable starting materials for the snack food. It would be a further advantage to the art when the processes may be operated with minimum of adjustments for various starting materials.